Because of commonly strong static charge build-up, plastic films have been hitherto often limited in their use other than the use taking advantage of such properties. For example, light-sensitive photographic materials commonly make use of plastic film as a support having electrical insulation properties. Such materials belong to what is called composite materials, comprised of a support and a light-sensitive photographic material layer. Hence the light-sensitive photographic materials tend to be statically charged when, during their manufacture and use, they come into contact with the surface of a material of the same or different kind or they are separated therefrom. Most static charges accumulated as a result of static charging cause various difficulties. The most important difficulty is what is called static marks, which are spots or branch-type or feather-type lines occurring during the photographic processing of the light sensitive photographic materials whose light-sensitive silver halide emulsion layers have been sensitized as a result of the discharge of static electricity accumulated before the photographic processing. When, for example, this phenomenon occurs in medical or industrial X-ray films, it leads to a very dangerous determination. This phenomenon becomes known only when the photographic films have been processed, and is one of very difficult problems. These accumulated static charges may also cause troubles such that dust adheres to a plastic film surface and no uniform coating on the film surface can be carried out.
Such troubles caused by static charging may also occur in many cases besides the foregoing. For example, in the course of manufacture, the troubles may be caused by contact friction between photographic films and rollers, and by separation of emulsion sides from support sides in the course of winding-up or unwinding of photographic films. In finished products, the troubles may be caused by separation of emulsion sides from base sides when photographic films are wound up and change-over is made, and by contact and separation occurring between X-ray films and machine parts during automatic photographing or between X-ray films and intensifying screens. The troubles may also be caused by contact with other packaging materials. The static marks of light-sensitive photographic materials, caused by accumulation of such static charges become remarkable with an increase in sensitivity of light-sensitive photo-graphic materials and an increase in processing speed thereof. In particular, in these days, static marks tend to occur since photographic materials have been made to have a higher sensitivity and are often handled under severe conditions such that light-sensitive coating is carried out at a higher speed, photographs are taken at a higher speed and automatic processing is carried out at a higher speed.
Moreover, in recent years, adhesion of dust to the photographic materials after photographic processing has come into question, and it is sought to make an improvement so that antistatic properties can also be retained after the processing.
The best method for eliminating such difficulties due to static is to increase electrical conductivity of materials so that static charges can be dissipated in a short time before the discharge of accumulated electricity takes place.
Accordingly, methods of improving the conductivity of supports of light-sensitive photographic materials or that of surface layers of various coatings have been hitherto proposed and it has been attempted to utilize various hygroscopic substances and water-soluble inorganic salts and certain types of surface active agents and polymers. For example, Japanese Patent Publication Open to Public Inspection [hereinafter referred to as Japanese Patent O.P.I. Publication] Nos. 91165/1974 and No. 121523/1974 disclose examples in which ion type polymers having a dissociative group in the polymer main chain are applied. Other invention is also known which relates to conductive polymers as disclosed in Japanese Patent O.P.I. Publication Nos. 9689/1990 and 182491/1990 and surface active agents as disclosed in Japanese Patent O.P.I. Publication Nos. 55541/1988, 148254/1988, 148256/1988 and 14191/1989.
These many substances, however, have a specificity depending on the types of film supports and the differences in photographic compositions and can give good results on certain types of film supports, photographic emulsions and other photographic components. They, however, not only can be of no use at all for antistatic in the case of other different types of film supports and photographic components, but also may adversely affect photographic performance. Another important disadvantage thereof is that these many substance lose their function as a conductive layer when used in an environment of low humidity.
For the purpose of preventing the deterioration of performance in an environment of low humidity, Japanese Patent Examined Publication Nos. 6616/1960 and 20735/1989 disclose techniques in which metal oxides are used as antistatic treatments. The former discloses a method in which a colloidal sol dispersion is used. The latter discloses a method in which a highly crystalline metal oxide powder having been treated at a high temperature is used so that a problem concerning conductivity in the former can be eliminated. In the latter technique, however, it is stated that, because of the use of a highly crystalline powder, its particle diameter and the ratio of particles to a binder must be taken into account as countermeasures to light scattering. Japanese Patent O.P.I. Publication No. 29134/1992 also discloses a method in which a particulate metal oxide and a fibrous metal oxide are employed as conductive materials used in light-sensitive photographic materials for the purpose of not only improving performance in an environment of low humidity but also eliminating other disadvantages. There, however, have remained a problem concerning the amount of the oxides added.
Thus, in relation to light-sensitive photographic materials provided with a layer containing conductive fine metal particles, problems have remained unsettled yet even though means for preventing the deterioration of performance in an environment of low humidity have been studied for 30 years or more since the above techniques were disclosed in Japanese Patent Examined Publication No. 6616/1960.
For example, in the case when a layer containing such conductive fine metal particles is provided adjoiningly to a silver halide layer containing silver halides, there is the problem that pressure marks or abrasion marks tend to occur in images as a result of any friction caused when light-sensitive photographic materials are handled. For another example, in the case when such particles are used as a mixture with a binder, there is the problem that fine particles present on the surface of light-sensitive photographic materials may fall as a result of any friction caused when light-sensitive photographic materials are manufactured or handled, and hence may adhere to rollers in the course of the manufacture to scratch the products being carried.
As a method for preventing the dust of metal oxide from falling and the silver halides from suffering pressure marks or abrasion marks, Japanese Patent O.P.I. Publication No. 104931/1982 discloses use of a metal oxide such as zinc oxide, stannic oxide or indium oxide in a backing layer. Since, however, metal oxides having conductivity are usually colored, fogging due to coloring may occur when contained in light-sensitive materials, to cause a great problem. According to the method disclosed in Japanese Patent O.P.I. Publication No. 104931/1982, any of these metal oxides must be used in an amount of about 1 g as described in Examples, and its coloring (dark blue) causes fog to greatly damage a photographic performance (light transmission).